This is compared to a higher and a lower reference value (Ref1, Ref2), said comparison providing an indication as to whether both of the gas discharge lamps (L1, L2) are the same type.

The reference value is dynamically set by the reference value setting unit on the basis of the required power amount.

At least a first reference value and a second reference value are selected for the second filter and used in filtering the block boundary.

Alternatively, dimunition is determined by forming a ratio of a reference average movement effort value and a contemporaneous movement effort value, and comparing the ratio against a threshold reference value.

S-SCH1 will comprise a reference sequence having a first index value and S-SCH2 will comprise a reference sequence having a second index value.

A rising reference value holding unit (703) and a trailing reference value holding unit (704) output a rising reference value and a trailing reference value, respectively.

The second reference index value is different than the first reference index value.

The value in the reference counter is compared to a configurable reference value.

The reference value is calculated as a function of other data sample(s) in the same pressure signal.

A reference value is calculated by subtracting the candidate pixel value and the median value (160).

Each threshold value is based on a current white reference value and a current black reference value.

A value obtained by subtracting the determined synchronization correction value from the reference value is set as a provisional reference value in the second reference signal generation unit.

The reference value is a measured pressure value.

reference value of an influencing quantity

reference value of an influencing factor